A multi-tube parallel packing oxidizer and a method for preparing isobutyric acid

Abstract

The application provides a multi-tube parallel filling oxidizer and a preparation method of isobutyric acid, and relates to the field of preparation of isobutyric acid. In the multi-tube parallel filling oxidizer, oxygen and isobutyraldehyde are countercurrently contacted, the contact efficiency is improved, and the oxidation reaction is rapidly reacted; and on the basis of circulating cooling water, an outer circulation heat exchange system is additionally arranged, so that the temperature of reactants can be better controlled, the occurrence of a side reaction is greatly reduced, and the product purity is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of isobutyric acid preparation, in particular to a multi-tube parallel packing oxidizer and a preparation method of isobutyric acid. BACKGROUND

[0002] Isobutyric acid is an important chemical, which plays a key role in the chemical industry, food and pharmaceutical fields. In the chemical industry, isobutyric acid is widely used in synthesis and reaction processes in the chemical industry; in the food field, isobutyric acid is mainly used as an acid taste regulator and food essence; in the pharmaceutical field, isobutyric acid can inhibit the growth and reproduction of some bacteria in some cases, and has a certain control effect on some bacterial infections and diseases.

[0003] The traditional method for preparing isobutyric acid is to directly oxidize isobutyraldehyde with air or oxygen, but the prepared isobutyric acid has low purity. SUMMARY

[0004] The present application provides a multi-tube parallel packing oxidizer and a preparation method of isobutyric acid. The prepared isobutyric acid has high purity.

[0005] The present application provides a multi-tube parallel packing oxidizer, which comprises a shell;

[0006] A pipe located inside the shell; the number of the pipe is greater than or equal to 2;

[0007] A first plate and a second plate embedded in the pipe, which block the space in the horizontal direction except the pipe body; the first plate and the second plate are located at the upper part and the lower part of the pipe, respectively;

[0008] A cooling water inlet and a cooling water outlet located between the first plate and the second plate;

[0009] A first distributor located at the top end of the pipe, which passes the reaction raw material into each pipe;

[0010] An external circulation heat exchanger and a second distributor;

[0011] The inlet of the external circulation heat exchanger is connected with the bottom of the shell, and the outlet of the external circulation heat exchanger is connected with the second distributor, so as to pass the reaction material through the external circulation heat exchanger into each pipe;

[0012] The second distributor is located between the first plate and the second plate;

[0013] A third distributor located below the second plate, which passes the oxidizing gas into each pipe.

[0014] Preferably, it further comprises a compressor;

[0015] The inlet of the compressor is connected with the shell above the first plate material, and the outlet of the compressor is connected with the inlet of the third distributor.

[0016] Preferably, the cooling water inlet is located below, and the cooling water outlet is located above.

[0017] Preferably, the method further comprises: a preheater and a compression pump connected with the preheater.

[0018] The compression pump is further connected with the first distributor.

[0019] The application also provides a preparation method of isobutyric acid, which is carried out in the multi-tube parallel packing oxidizer.

[0020] The isobutyraldehyde is continuously introduced into each tube through the first distributor, and the oxygen is continuously introduced into each tube through the third distributor to perform a first oxidation reaction, and the continuously generated crude isobutyric acid is introduced into the external circulation heat exchanger to perform heat exchange and then continuously introduced into each tube through the second distributor to perform a second oxidation reaction, so that the isobutyric acid is obtained.

[0021] Preferably, the gas-liquid ratio of the isobutyraldehyde and the oxygen is 4-8:1.

[0022] Preferably, the sum of the time of the first oxidation reaction and the second oxidation reaction is 1-1.5 h.

[0023] Preferably, the flow rate of the oxygen is 700-900 mL / min, and the flow rate of the isobutyraldehyde is 120-160 mL / min.

[0024] Preferably, the temperature of the crude isobutyric acid and the isobutyric acid is independently 25-55℃.

[0025] Preferably, the pressure of the first oxidation reaction and the second oxidation reaction is 0.3-0.5 MPa.

[0026] The application provides a multi-tube parallel packing oxidizer, which comprises a shell.

[0027] The tubes are located in the shell; the number of the tubes is greater than or equal to 2.

[0028] The first plate material and the second plate material are embedded in the tubes to block the space in the horizontal direction except the tubes; the first plate material and the second plate material are respectively located at the upper part and the lower part of the tubes.

[0029] The cooling water inlet and the cooling water outlet are located between the first plate material and the second plate material.

[0030] The first distributor is located at the top end of the tubes to introduce the reaction raw materials into each tube.

[0031] An outer circulation heat exchanger and a second distributor;

[0032] The inlet of the outer circulation heat exchanger is connected with the bottom of the shell, and the outlet of the outer circulation heat exchanger is connected with the second distributor, so that the reactants passing through the outer circulation heat exchanger are introduced into each tube;

[0033] The second distributor is located between the first plate and the second plate;

[0034] A third distributor located below the second plate introduces the oxidizing gas into each tube.

[0035] The multi-tube parallel packing oxidizer of the present application can make the oxygen and isobutyl aldehyde contact in countercurrent, improve the contact efficiency, make the oxidation reaction react rapidly, and on the basis of circulating cooling water, the outer circulation heat exchange system is additionally installed to better control the temperature of the reactants, greatly reduce the occurrence of side reactions, and improve the product purity.

[0036] The multi-tube parallel packing oxidizer of the present application is easy to control.

[0037] Further, the present application further improves the purity of isobutyric acid by adjusting the gas-liquid ratio of oxygen and isobutyl aldehyde, the temperature of crude isobutyric acid, the time and pressure of the oxidation reaction. The results of the examples show that the preparation method of the present application makes the isobutyl aldehyde oxidation rate reach about 95%, which exceeds the development level at the same period, and compared with the existing kettle type and tubular production process, the method reduces the reaction time while improving the isobutyl aldehyde conversion rate.

[0038] The temperature and pressure of the preparation method of the present application are relatively mild, the process safety is strong, and the product stability is good. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 It is the process flow chart of the embodiment of the present application;

[0040] Figure 2 It is the isobutyric acid gas chromatogram when the oxygen flow is 500 mL / min in Example 1;

[0041] Figure 3 It is the isobutyric acid gas chromatogram when the oxygen flow is 700 mL / min in Example 1;

[0042] Figure 4 It is the isobutyric acid gas chromatogram when the oxygen flow is 900 mL / min in Example 1;

[0043] Figure 5 It is the isobutyric acid gas chromatogram when the reaction time is 0.5 h in Example 2;

[0044] Figure 6Gas chromatogram of isobutyric acid when the reaction time is 1 h in Example 2;

[0045] Figure 7 Gas chromatogram of isobutyric acid when the reaction time is 1.5 h in Example 2;

[0046] Figure 8 Gas chromatogram of isobutyric acid when the reaction time is 1 h in Example 2;

[0047] Figure 9 Gas chromatogram of isobutyric acid when the reaction time is 1.5 h in Example 2;

[0048] Figure 10 Gas chromatogram of isobutyric acid when the reaction time is 1 h in Example 2;

[0049] Figure 11 Gas chromatogram of isobutyric acid when the reaction time is 1.5 h in Example 2;

[0050] Figure 12 Gas chromatogram of isobutyric acid when the reaction time is 1 h in Example 2. DETAILED DESCRIPTION

[0051] The application provides a multi-tube parallel packing oxidizer, which comprises a shell;

[0052] tubes located inside the shell; the number of the tubes is greater than or equal to 2;

[0053] a first plate and a second plate embedded in the tubes to block the space above and below the tubes in the horizontal direction; the first plate and the second plate are respectively located at the upper part and the lower part of the tubes;

[0054] a cooling water inlet and a cooling water outlet located between the first plate and the second plate;

[0055] a first distributor located at the top end of the tubes to pass the reaction raw materials into each tube;

[0056] an external circulation heat exchanger and a second distributor;

[0057] the inlet of the external circulation heat exchanger is connected with the bottom of the shell, the outlet of the external circulation heat exchanger is connected with the second distributor, and the reaction materials passing through the external circulation heat exchanger are passed into each tube;

[0058] the second distributor is located between the first plate and the second plate;

[0059] a third distributor located below the second plate to pass the oxidizing gas into each tube.

[0060] In the present application, the multi-tube parallel packing oxidizer comprises a shell;

[0061] In an embodiment of the present application, the shell has an inner diameter of 14 cm;

[0062] In the present application, the multi-tube parallel packing oxidizer comprises tubes inside the shell; the number of the tubes is ≥ 2;

[0063] In an embodiment of the present application, the number of the tubes is 7, the inner diameter of the tubes is 2 cm; the tubes are filled with ceramic packing. The ceramic packing is preferably ceramic Pall ring packing with a specification of 25 mm*25 mm*3 mm.

[0064] In the present application, the multi-tube parallel packing oxidizer comprises a first plate and a second plate embedded in the tubes to block the space other than the tubes in the horizontal direction; the first plate and the second plate are respectively located at the upper part and the lower part of the tubes. The blocked space can be supplied with cooling water to cool the tubes.

[0065] In the present application, the multi-tube parallel packing oxidizer comprises a cooling water inlet and a cooling water outlet between the first plate and the second plate;

[0066] In an embodiment of the present application, the cooling water inlet is located below and the cooling water outlet is located above.

[0067] In the present application, the multi-tube parallel packing oxidizer comprises a first distributor at the top end of the tubes to supply reaction raw materials into each tube.

[0068] In the present application, the multi-tube parallel packing oxidizer comprises an external circulation heat exchanger; the inlet of the external circulation heat exchanger is connected with the bottom of the shell, and the outlet of the external circulation heat exchanger is connected with the second distributor to supply the reaction material through the external circulation heat exchanger into each tube.

[0069] In the present application, the multi-tube parallel packing oxidizer comprises an external circulation heat exchanger and a second distributor;

[0070] The inlet of the external circulation heat exchanger is connected with the bottom of the shell, and the outlet of the external circulation heat exchanger is connected with the second distributor to supply the reaction material through the external circulation heat exchanger into each tube;

[0071] The second distributor is located between the first plate and the second plate.

[0072] In the present application, the multi-tube parallel packing oxidizer comprises a third distributor below the second plate to supply oxidation gas into each tube.

[0073] In one embodiment of the present application, the multi-tube parallel packing oxidizer further comprises a compressor;

[0074] The inlet of the compressor is connected to the shell above the first plate material, and the outlet of the compressor is connected to the inlet of the third distributor. The excess oxygen at the top of the multi-tube parallel packing oxidizer is pressurized by the compressor and recycled, and passes through the discharge port and the feed port, realizing continuous reaction and avoiding the problems of high energy consumption, serious pollution, long time consumption and harsh reaction conditions in the traditional production process.

[0075] The present application also provides a preparation method of isobutyric acid, which is carried out in the multi-tube parallel packing oxidizer described in the above technical solution, and comprises the following steps:

[0076] The continuously generated crude isobutyric acid is passed into each tube through the first distributor and the third distributor for first oxidation reaction, and then passed into the outer circulation heat exchanger for heat exchange and then continuously passed into each tube through the second distributor for second oxidation reaction, so that the isobutyric acid is obtained.

[0077] Before the isobutyraldehyde is continuously passed into each tube through the first distributor and the oxygen is continuously passed into each tube through the third distributor, the present application preferably further comprises: discharging the gas in the multi-tube parallel packing oxidizer by using oxygen, and passing in circulating cooling water.

[0078] In the present application, the pressure in the multi-tube parallel packing oxidizer after discharging the gas is preferably 0.3-0.5 MPa; and the temperature of the cooling water is preferably 15-20℃.

[0079] In the present application, after discharging the gas, the isobutyraldehyde is preferably passed into the third distributor through a preheater and a compression pump.

[0080] In the present application, the temperature of the isobutyraldehyde after preheating is preferably 35℃.

[0081] In the present application, the flow rate of the oxygen is preferably 700-900 mL / min, and the flow rate of the isobutyraldehyde is preferably 120-160 mL / min, more preferably 130-150 mL / min; and the gas-liquid ratio of the isobutyraldehyde to oxygen is preferably 4-8:1, more preferably 5-6:1.

[0082] In the present application, the pressure of the first oxidation reaction and the second oxidation reaction is 0.3-0.5 MPa, more preferably 0.4-0.45 MPa. In the present application, the temperature of the crude isobutyric acid and the isobutyric acid without passing through the outer circulation heat exchanger is independently 35-55℃, preferably 40-45℃.

[0083] In the present application, the sum of the time of the first oxidation reaction and the second oxidation reaction is preferably 1-1.5 h.

[0084] The multi-tube parallel packing oxidizer, the isobutyric acid preparation method provided by the application will be described in detail in combination with the embodiments below, but they cannot be understood as the limitation of the protection scope of the application.

[0085] A multi-tube parallel packing oxidizer, comprising:

[0086] A shell; the inner diameter of the shell is 14 cm;

[0087] Tubes located inside the shell; the number of the tubes is 7; the inner diameter of the tubes is 2 cm; the tubes are fully filled with ceramic Pall ring packing with the specification of 25 mm*25 mm*3 mm;

[0088] First and second plates embedded in the tubes to block the space other than the tubes in the horizontal direction; the first and second plates are located at the upper and lower parts of the tubes respectively;

[0089] A cooling water inlet and a cooling water outlet located between the first and second plates; the cooling water inlet is located at the lower part, and the cooling water outlet is located at the upper part.

[0090] A first distributor located at the top end of the tubes to pass the reaction raw materials into each tube;

[0091] An external circulation heat exchanger and a second distributor;

[0092] The inlet of the external circulation heat exchanger is connected with the bottom of the shell, and the outlet of the external circulation heat exchanger is connected with the second distributor to pass the reaction materials through the external circulation heat exchanger into each tube;

[0093] The second distributor is located between the first and second plates;

[0094] A third distributor located below the second plate to pass the oxidizing gas into each tube;

[0095] A compressor;

[0096] The inlet of the compressor is connected with the shell above the first plate, and the outlet of the compressor is connected with the inlet of the third distributor.

[0097] Figure 1 The process flow chart of the embodiment of the application.

[0098] Embodiment 1

[0099] (1) First, use oxygen to exhaust the gas in the multi-tube parallel packing oxidizer;

[0100] (2) Control different oxygen flow rates of 500, 700, and 900 mL / min in multiple experiments, and increase the system pressure to 0.4 MPa and keep it constant;

[0101] (3) The isobutyl aldehyde is preheated to 35°C by the material circulating pump, and then pumped into the multi-tube parallel packed oxidizer at a speed of 140 mL / min;

[0102] (4) The external circulating cooling water is set to 15°C, and the reaction heat is removed in time;

[0103] (5) The crude isobutyric acid at the bottom of the oxidizer is subjected to external circulation heat exchange, and then reenters the multi-tube parallel packed oxidizer, and the crude isobutyric acid temperature is controlled at 40°C;

[0104] (6) The excess oxygen is discharged from the top of the oxidizer, and the oxygen is pressurized by a compressor and then pumped into the oxidizer for recycling;

[0105] (7) Oxygen is continuously introduced to maintain the stability of the internal pressure of the device;

[0106] (8) The reaction is continuously carried out for 1 h, and the product composition is analyzed by sampling from the bottom of the oxidizer when the outlet temperature of the device is stable.

[0107] The isobutyl aldehyde conversion rates under oxygen flow rates of 500, 700, and 900 mL / min were investigated, and the results were reflected by gas chromatography data, as shown in Figures 2-4 and Table 1. Among them, Figure 2 is the isobutyric acid gas chromatogram when the oxygen flow rate is 500 mL / min; Figure 3 is the isobutyric acid gas chromatogram when the oxygen flow rate is 700 mL / min; Figure 4 is the isobutyric acid gas chromatogram when the oxygen flow rate is 900 mL / min.

[0108] Table 1 Gas chromatography data of isobutyric acid in Example 1

[0109] Number Retention time Area Peak Area % Figure 2 12.539 45203759 3079659 74.463 Figure 3 12.539 52664062 3561252 93.892 Figure 4 12.468 46989051 3063106 85.245

[0110] As shown in Table 1, Figures 2-4 when the oxygen flow rate is 700 mL / min, the content of isobutyric acid in the product is the highest, which is 93.892%; when the oxygen flow rate is 700 mL / min, the content of isobutyric acid decreases due to the decrease of oxygen flow rate; when the oxygen flow rate is 700 mL / min, the increase of oxygen causes the reaction to intensify, resulting in the increase of by-products, which leads to the decrease of the content of isobutyric acid in the product.

[0111] Example 2

[0112] (1) First, use oxygen to discharge the gas in the multi-tube parallel packed oxidizer;

[0113] (2) The oxygen flow rate was controlled at 700 mL / min, and the system pressure was raised to 0.4 MPa and kept constant;

[0114] (3) The isobutyl aldehyde was preheated to 35°C by the material circulating pump and continuously pumped into the multi-tube parallel packed oxidizer at a speed of 140 mL / min;

[0115] (4) The external circulating cooling water was set at 15°C, and the reaction heat was removed in time;

[0116] (5) The crude isobutyric acid at the bottom of the oxidizer was re-entered into the multi-tube parallel packed oxidizer after external circulation heat exchange, and the crude isobutyric acid temperature was controlled at 40°C;

[0117] (6) The excess oxygen was discharged from the top of the oxidizer, and the oxygen was pressurized by a compressor and then pumped into the oxidizer for recycling;

[0118] (7) Oxygen was continuously introduced to maintain the stable pressure inside the device;

[0119] (8) Different reaction times of 0.5, 1, and 1.5 h were controlled in multiple tests, and the product composition was analyzed by sampling from the bottom of the oxidizer when the device outlet temperature was stable.

[0120] The isobutyl aldehyde conversion rate under different reaction times was explored, and the results were reflected by gas chromatography data as shown in Figures 5-7 and Table 2. Among them, Figure 5 is the isobutyric acid gas chromatogram when the reaction time is 0.5 h;

[0121] Figure 6 is the isobutyric acid gas chromatogram when the reaction time is 1 h; Figure 7 is the isobutyric acid gas chromatogram when the reaction time is 1.5 h.

[0122] Table 2 Gas chromatography data of isobutyric acid of Example 2

[0123] Number Retention time Area Peak Area % Figure 5 12.596 35057518 2716423 58.732 Figure 6 12.529 52308842 3550206 92.866 Figure 7 12.562 47955077 3377229 82.781

[0124] As shown in Table 2, Figures 5-7 when the reaction time is 1 h, the content of isobutyric acid in the product is the highest, which is 92.866%; when the reaction time is 0.5 h, the reaction is incomplete due to the short reaction time, and the content of isobutyric acid decreases significantly; when the reaction time is 1.5 h, the side reaction increases due to the long reaction time, which leads to the increase of by-products, resulting in the decrease of the content of isobutyric acid in the product.

[0125] Example 3

[0126] Experiments were carried out using a conventional batch oxidizer (compared with the pipe-in-parallel packed oxidizer of the present application: the conventional batch oxidizer does not contain the first plate, the second plate, the first distributor, the pipe, the external circulation heat exchanger, the second distributor and the third distributor) and the pipe-in-parallel packed oxidizer respectively:

[0127] When the conventional batch oxidizer was used, 2000 mL of isobutyl aldehyde was added into the oxidizer, which was 1 / 4 of the total volume, the gas in the oxidizer was discharged by passing oxygen, the pressure of the system was increased to 0.4 MPa and then kept constant, the cooling water was circulated for heat exchange (the temperature of the condensate water was 15 ℃), the oxygen flow was controlled at 700 mL / min and was passed from the top, and after 1 h, sampling was carried out;

[0128] When the pipe-in-parallel packed oxidizer was used:

[0129] (1) the oxygen was passed to discharge the gas in the oxidizer, the oxygen flow was controlled at 700 mL / min, and the pressure of the system was increased to 0.4 MPa and then kept constant;

[0130] (2) the isobutyl aldehyde was preheated to 35 ℃ by the material circulation pump and was continuously pumped into the pipe-in-parallel packed oxidizer at a speed of 140 mL / min;

[0131] (3) the external circulation cooling water was set at 15 ℃ (the flow rate of the cooling water was the same as that when the conventional batch oxidizer was used), and the reaction heat was removed in time;

[0132] (4) the crude isobutyric acid at the bottom of the oxidizer was subjected to external circulation heat exchange and then re-entered the pipe-in-parallel packed oxidizer, and the temperature of the crude isobutyric acid was controlled at 40 ℃;

[0133] (5) the excess oxygen was discharged from the top of the oxidizer, and the oxygen was pressurized by using a compressor and then was pumped into the oxidizer for recycling;

[0134] (6) the oxygen was continuously passed to keep the pressure in the device stable;

[0135] (7) the reaction was continuously carried out for 1 h, the sampling was carried out from the bottom of the oxidizer when the temperature of the device was stable, and the product composition was analyzed.

[0136] The isobutyl aldehyde conversion rates under different reaction devices were explored, and the results were reflected by gas chromatography data, such as Figures 8-9 , wherein Figure 8 is the isobutyric acid gas chromatogram of the conventional batch oxidizer; Figure 9 is the isobutyric acid gas chromatogram of the pipe-in-parallel packed oxidizer of the present application.

[0137] Table 3 isobutyric acid gas chromatography data of Example 3

[0138] Number Retention time Area Peak Area % Figure 8 12.605 38741899 2888563 65.943 Figure 9 12.538 53389331 3587107 93.594

[0139] From Table 3, Figures 8-9 It can be seen that when using a conventional batch oxidizer, the content of isobutyric acid in the product is low, 65.943%, and it is difficult to control the reaction temperature in the batch reactor, resulting in intense side reactions and reduced isobutyric acid purity; when using a multi-tube parallel packed oxidizer, the content of isobutyric acid in the product is higher, 93.594%, which can better control the system temperature and remove the reaction heat in time to inhibit the occurrence of side reactions.

[0140] Example 4

[0141] (1) First, use oxygen to discharge the gas in the multi-tube parallel packed oxidizer;

[0142] (2) Control the oxygen flow to 700 mL / min, and raise the system pressure to 0.4 MPa and keep it constant;

[0143] (3) The material circulating pump preheats the isobutyraldehyde to 35℃ and continuously pumps it into the multi-tube parallel packed oxidizer at a speed of 140 mL / min;

[0144] (4) The external circulating cooling water is set to 15℃ to remove the reaction heat in time;

[0145] (5) The crude isobutyric acid at the bottom of the oxidizer is reheated by external circulation and then reenters the multi-tube parallel packed oxidizer, and the crude isobutyric acid temperature is controlled at 30℃, 40℃, and 50℃ respectively in multiple experiments;

[0146] (6) The excess oxygen is discharged from the top of the oxidizer, and the compressor is used to pressurize the oxygen and then pump it back into the oxidizer for recycling;

[0147] (7) Continuously pass in oxygen to keep the internal pressure of the device stable;

[0148] (8) Continue to react for 1 h, and when the outlet temperature of the device is stable, take samples from the bottom of the oxidizer and analyze the product composition.

[0149] The conversion rate of isobutyraldehyde at different outlet temperatures was explored, and the results were reflected by gas chromatography data, as shown in Figures 10-12 , wherein Figure 10 is the isobutyric acid gas chromatogram when the crude isobutyric acid temperature is 30℃; Figure 11 is the isobutyric acid gas chromatogram when the crude isobutyric acid temperature is 40℃; Figure 12 is the isobutyric acid gas chromatogram when the crude isobutyric acid temperature is 50℃.

[0150] Table 4 Isobutyric acid gas chromatography data of Example 4

[0151] Number Retention time Area Peak Area % Figure 10 12.678 22172301 2024520 37.284 Figure 11 12.522 55997521 3736374 93.449 Figure 12 12.566 46876057 3325833 80.700

[0152] From Table 4, Figures 10-12 It can be seen that when the external circulation reflux temperature is controlled at 40℃, the content of isobutyric acid in the product is the highest, which is 93.449%; when the external circulation reflux temperature is controlled at 30℃, the reaction is incomplete due to the lower temperature, and the content of isobutyric acid is greatly reduced; when the external circulation reflux temperature is controlled at 50℃, the side reaction is intensified due to the too high reaction temperature, which causes the increase of by-products, resulting in the decrease of the content of isobutyric acid in the product.

[0153] The above only describes the preferred embodiments of the present application, and it should be noted that for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A process for the preparation of isobutyric acid, characterized in that, In a multi-tube parallel packed oxidizer, the steps are: The gas in the multi-tube parallel packed oxidizer is discharged by oxygen, and after circulating cooling water is introduced, isobutyl aldehyde is continuously introduced into each tube through the first distributor, oxygen is continuously introduced into each tube through the third distributor to carry out the first oxidation reaction, and the continuously generated crude isobutyric acid is introduced into the external circulation heat exchanger to exchange heat and then continuously introduced into each tube through the second distributor to carry out the second oxidation reaction, to obtain the isobutyric acid; The multi-tube parallel packed oxidizer comprises a shell; The tubes located inside the shell; the number of the tubes is ≥2; the tubes are filled with ceramic packing; The first plate and the second plate embedded in the tubes block the space in the horizontal direction except the tube body; the first plate and the second plate are located at the upper part and the lower part of the tubes, respectively; The cooling water inlet and the cooling water outlet located between the first plate and the second plate; The first distributor located at the top end of the tube introduces the reaction raw material into each tube; The external circulation heat exchanger and the second distributor; The inlet of the external circulation heat exchanger is connected with the bottom of the shell, and the outlet of the external circulation heat exchanger is connected with the second distributor, so that the reactant passing through the external circulation heat exchanger is introduced into each tube; The second distributor is located between the first plate and the second plate; The third distributor located below the second plate introduces the oxidation gas into each tube; The sum of the time of the first oxidation reaction and the second oxidation reaction is 1h; The gas-liquid ratio of the oxygen and the isobutyl aldehyde is 5:1; The temperature of the crude isobutyric acid is 40℃.

2. The production method according to claim 1, characterized by, The multi-tube parallel packed oxidizer further comprises a compressor; The inlet of the compressor is connected with the shell above the first plate, and the outlet of the compressor is connected with the inlet of the third distributor.

3. The preparation method according to claim 1, characterized in that, The cooling water inlet is located below, and the cooling water outlet is located above.

4. The preparation method according to claim 1, characterized in that, The multi-tube parallel packed oxidizer further comprises a preheater and a compression pump connected with the preheater; The compression pump is also connected with the first distributor.

5. The preparation method according to claim 1, characterized in that, The flow rate of the oxygen is 700~900mL / min, and the flow rate of the isobutyl aldehyde is 120~160mL / min.

6. The method of claim 1, wherein the method is characterized by, The temperature of the isobutyric acid is 25~55℃.

7. The method of claim 1, wherein the method is characterized by, The pressure of the first oxidation reaction and the second oxidation reaction is 0.3~0.5MPa.

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